JPS63100730A - Mask for photoelectron transfer - Google Patents

Abstract

PURPOSE:To manufacture a mask for photoelectron transfer assuring stable photoelectron quantity by a method wherein a metal is patterned on a transparent substrate and after sputtering Ag thereon, alkali metal or alkali earth metal is further evaporated thereon. CONSTITUTION:Metallic patterns 12 such as Cr etc. in film thickness of 600-2000Angstrom are made on a transparent substrate 11 such as of quartz etc. Ag is not diffused in the metallic patterns 12. First, Ag is sputtered on the overall surface in thickness of around 50-600Angstrom A. Second, when the Ag surface is heated up to 100-200 deg.C to vacuum-evaporate a Cs film 14, the reaction of Ag to Cs is accelerated to stabilize the Cs. Through these procedures, the serviceable wavelength of far ultraviolet rays for Ag as a photoelectric material can be increased up to 3500-4000Angstrom compared with conventional CsI to improve the resolving power so that the light quantity may be extremely stabilized to increase the serviceable times of mask.

Description

[Detailed Description of the Invention] [Summary] Metal is patterned on a transparent substrate, and silver (Ag
) and an alkali metal or alkaline earth metal is deposited on the Ag film.

[Industrial application field]

The present invention relates to a photoelectron transfer mask and its manufacturing method. More specifically, the present invention relates to a photoelectron transfer mask and a method for manufacturing the same. More specifically, the present invention uses silver, which has not been conventionally used as a photoelectron source, and coats the surface of the silver with an alkali metal or alkaline earth metal, such as cesium. The present invention relates to photoelectronic transfer masks of deposited structures and methods of making such masks.

[Conventional technology]

Microfabrication processes are important in the production of VLSIs, and one of the microfabrication techniques (lithography techniques) is a technique for transferring micropatterns onto wafers and the like. Conventionally, as a transfer technology for such fine patterns, light (wavelength of about 40
00 people) and using the reticle as the original 5:1,10;
A method of performing reduction projection exposure of the first order is known. However, with this method, as the pattern becomes finer, blurring of the transferred image due to diffraction, interference, etc. is unavoidable, and the resolution is reduced to 0.8.
It is said that it is extremely difficult to raise it above μ ugliness.

Electron beam exposure method to improve resolution.

Techniques such as X-ray exposure method and photoelectron transfer method are known.

In electron beam exposure, an electron beam having a dotted or rectangular cross section is deflected, irradiated onto a wafer without changing its position, and a fine pattern is drawn on the wafer in conjunction with the movement of a stage. Therefore, in addition to an electron source, a column for converging, shaping, and deflecting the electron beam, and a stage for supporting the wafer and changing the exposure position, a system for controlling these is required. This method can improve resolution, but because it uses a so-called "-brush writing" type of exposure based on a huge amount of pattern data, it takes time to expose, has low processing capacity (throughput), and is not suitable for mass production. is not suitable.

For example, the X-ray exposure method uses 10 to 50 K11.
This is a proximity exposure method that uses a jl light source and uses X-rays with a wavelength of 1 to 10 people. Therefore,
In addition to the light source described above, X-ray exposure requires a combination of an aligner that supports the mask and wafer and can align them with high precision. In this respect, it is similar to conventional optical exposure, but as mentioned above, the value becomes high due to the presence of the light source, and the relationship between the absorption coefficient with respect to the light source wavelength requires consideration of the mask constituent materials, and furthermore, it is a proximity exposure. Therefore, as the diameter of the wafer increases, problems such as blurring occur due to variations in the gap between the mask and the wafer due to warping of the mask and wafer. Although it has been proposed to use synchrotron radiation as the light source for generating X-rays, it is difficult to use it efficiently since the equipment is very heavy, and it cannot be said that it is suitable for mass production.

A photoelectronic transfer method is an exposure method that takes advantage of both the high throughput of transfer methods and the high resolution of electron beams. There are methods for photoelectronic transfer as described below.

The 1:1 (equal magnification) transfer technique using an electron beam transfers a mask image onto a sample using an electron beam, and its principle is shown in FIG. Focusing coil (Helmholtz coil, etc.) 31
A photoelectric (photocathode) mask 32 and a sample (for example, a silicon wafer 37 whose surface is coated with an electronic resist 36) are placed perpendicularly to the magnetic field in a parallel magnetic field (in the vertical direction in the figure) created by
are placed facing each other in parallel, and a voltage is applied such that the mask is negative and the sample is positive. The photoelectric mask 32 is made by forming a pattern to be transferred consisting of an ultraviolet absorber 34 (for example, chromium, Cr) on a transparent substrate, for example, a quartz plate 33, and forming a photoelectric material film on which electrons are emitted by irradiation with ultraviolet rays. A cathode 35 is made (by evaporating cesium iodide (Cs) over the entire surface in a vacuum).

When the ultraviolet rays 39 emitted by the ultraviolet source 38 are irradiated from above the quartz plate 33, the ultraviolet rays hit the photoelectric material in areas where there is no pattern (where there is no ultraviolet absorber 34), and electrons 40 are emitted from that area as shown by the arrow. . Electrons 40 emitted from one point on the mask 32 travel in a spiral toward the sample due to the electric field created by the polarizing coil 41 there and the parallel magnetic field created by the focusing coil 31, and converge again at one point at a certain point. In other words, focus.

FIG. 3 shows a part of the device structure, with a photoelectric mask 32 facing each other on the right side of the center of the figure, and a silicon wafer 37 on the left side. The X-ray detector 40 on the left side of the wafer is used to perform alignment by detecting a line when electrons emitted from the alignment mark on the mask hit a heavy metal mark on the wafer. The polarizing coil 41 polarizes the electron beam emitted from the mask and is used to align the mask pattern and the pattern on the wafer.

[Problem that the invention seeks to solve]

Conventionally, a mask using Csl as a transmission type photoelectronic transfer mask, that is, a photoelectronic material, is known. but,
Csl has a short light absorption edge (it has a high work function, which is the height of the potential barrier that must be overcome at the surface for electrons to escape from Csl), and its particles are rough. It easily absorbs moisture, is unstable, and easily disturbs the pattern, and its use is limited to 20 to 50 exposures.

The present invention was created in view of these points, and an object of the present invention is to provide a photoelectronic transfer mask that can obtain a stable amount of photoelectrons, and a method for manufacturing the same.

[Means for solving problems]

FIG. 1 is a partial sectional view of an embodiment of the present invention, and in the figure, 11
1 is a transparent substrate, 12 is a metal pattern, 13 is AgPA, 1
4 is C5Il! attached to the surface of the Ag film 13! It is.

In the present invention, chromium (Cr) is deposited on a light-transparent substrate made of quartz, sapphire, ruby, or the like.

A metal pattern 12 of tantalum (Ta), tungsten (W), etc. is made, and a transparent substrate 1 containing the metal pattern 12 is formed.
A photoelectronic transfer mask is provided, in which silver is deposited on the Ag film 1 to form an Ag film 3, and an alkali metal or alkaline earth metal is deposited on the Ag film 13 to form the deposited film 14. Cesium (Cs) is preferable as the alkali metal, and barium (Ba) is preferable as the alkaline earth metal.

[Effect]

Ag is more stable as a photoelectric substance than Csl, and the wavelength that can be used for far ultraviolet light is 1930 to 240 in the case of Csl.
While there are 0 people, 8g has 3500 to 4000 people, which improves the resolution.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

In the present invention, the transparent substrate 11 shown in FIG. 1 is made of a material that transmits light, such as quartz, sapphire, or ruby. The case where Cs is used as the alkali metal will be described.

Metal (Cr) is deposited on the transparent substrate 11, for example, by vapor deposition.

(Ta, W, etc.) is deposited and patterned to form the metal pattern 12. Such a metal has the advantage that A does not diffuse when heated.The thickness of the metal pattern 12 is set to a thickness of 600 to 2,000 to sufficiently absorb light, that is, to sufficiently block light. do. If it is thinner than 600, it will not be able to block the light sufficiently,
Even if the thickness is made thicker than 2,000 mm, a particularly remarkable light absorption effect cannot be obtained, so it is wasteful to make it thicker than that.

Next, Ag is deposited to a thickness of 50 to 600 layers on the transparent substrate including the metal pattern 12 by vapor deposition or sputtering to form an Ag film 13. The reason for this is that if the thickness is thinner than 50 mm, light will pass through and the pattern transferred onto the sample by exposing the sample will be disturbed, and if the thickness is greater than 600 mm, the photoelectron emission will decrease. This is because light is absorbed far before the light (on the incident side) and no longer contributes to photoelectron emission. 1N oxide (Ag-0) is generally well known as a photoelectric material, but the complexity of the oxidation process and
It is difficult to control the degree of oxidation thickness,
Since it is difficult to use as a material for a photoelectronic transfer mask, an Ag film having the thickness described above was used.

Next, Cs is deposited in a vacuum to form a Cs film 14. Cs may be deposited by creating a Cs ion source and depositing Cs with an ion beam, or by reducing the Cs compound and extracting only Cs and depositing it. For this purpose, there is a method using a Ta boat. According to the inventor's experiments, when depositing Cs on the Ag film, the heg film surface was
It was confirmed that heating within the range of 00 to 200°C promoted the reaction between Ag and Cs, stabilized Cs, and as a result, photoelectrons could be stably extracted. At a temperature lower than 100°C, the reaction between Ag and Cs is significantly slowed down, and even when heated to a temperature higher than 200°C, no significant change occurs in the reaction between Ag and Cs.

〔Effect of the invention〕

As described above, according to the present invention, the Ag-Cs structure mask made by the method described above not only provides an extremely stable amount of photoelectrons, but also allows for one pattern to be replaced for a predetermined batch. The throughput of the exposure process has been significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. 2 and 3 are sectional views of a conventional example. In Figure 1, 11 is a transparent substrate; 12 is a metal pattern, 13 is an Ag film; 14 is a Cs film. Agent: Patent attorney: Akira Kukimoto Sub-Agent Patent Attorney Yoshiyuki Osuga Fertility Analysis 1 Criticism Figure 1

Claims (6)

[Claims] (1) A metal pattern (12) for light absorption is provided on a transparent substrate (11), a silver film (13) is formed on the entire surface of the substrate (11) including the metal pattern (12), and the silver film (13) A photoelectronic transfer mask having a structure on which a film (14) made of an alkali metal or an alkaline earth metal is formed. (2) The mask according to claim 1, wherein the transparent substrate (11) is made of quartz, sapphire, or ruby. (3) The mask according to claim 1, wherein the metal pattern (12) is made of chromium, tantalum, or tungsten. (4) The mask according to claim 1, wherein the silver film (13) has a thickness within the range of 50 to 600 Å. (5) A step of depositing a film of a light-absorbing substance on the transparent substrate (11) and patterning it to form a metal pattern (12); depositing a silver film (1) on the substrate (11) including the metal pattern (12);
3) and a step of depositing an alkali metal or an alkaline earth metal onto the silver film (13). (6) In the above-mentioned cesium deposition, the Ag film (13
6. The method according to claim 5, wherein the surface of the substrate is heated to a temperature within the range of 100 to 200°C.